The objectives of this project are to investigate the structure, biosynthesis, and secretion of lipoteichoic acids and the role of lipoteichoic acids in plaque formation. Such aims can be achieved by studying the structure, mechanism of biosynthesis and secretion of lipoteichoic acids in Streptococcus sanguis and the role of lipoteichoic acid in the adherence of cells on the tooth surface. S. sanguis is known to be the major streptococcal inhabitants on human tooth surface. We have found recently that there are large quantities of lipoteichoic acids present in the cell membrane and cell wall of S. sanguis. Our pulse chase study suggested that phosphatidylglycerol is a precursor for the synthesis of lipoteichoic acids. Moreover, the lipoteichoic acids were actively secreted into culture medium. Due to the amphipathic nature and high phosphate content of lipoteichoic acids, they may play important roles in the adherence of bacterial cells on the tooth surface. In this project the following four specific objectives will be pursued: (1) The structure of lipoteichoic acids. Attention will be focused on the structure of lipid moiety and glucosidic linkages. (2) Mechanism of lipoteichoic acid biosynthesis. In vitro system will be utilized to elucidate the stepwise reactions involved in the synthesis of membrane lipoteichoic acid. (3) The effects of various conditions on the secretion of lipoteichoic acids. The effects of pH, aeration, growth rate, on the secretion of lipoteichoic acids will be investigated. (4) The role of lipoteichoic acids on the adherence of bacterial cells on tooth surface. S. sanguis is known to possess a strong adherence ability to the tooth surface. The effect of purified lipoteichoic acid, lipoteichoic acid binding factors and antilipoteichoic acid antibody on the adherence of S. sanguis to enamel powder and the tooth surface will be investigated.